This invention relates to fault diagnostics in electronic circuits. More particularly, this invention relates to methods and arrangements for communicating fault diagnostics to repair systems.
VLSI technology permits fairly complex subsystems to be packaged on removable, or pluggable, circuit packs. The cost of a circuit board increases with complexity, and complexity increases with advances in VLSI manufacturing technologies.
High circuit board costs make repair of failed circuit boards desirable, but the complexity that comes with VLSI makes field repair almost impossible. Consequently, many current system designs incorporate methods and hardware means for isolating faults to removable sub-assembly (e.g., a circuit board), and rely on a field technician to locate the failed sub-assemblies, replace them, and send the failed units to repair centers.
In some software-based systems, diagnostic software is also incorporated which is activated either automatically, or manually, and that software exercises the system and locates the faults to within the desired granularity. Typically, the desired granularity is the removable circuit board. In most of these applications, detailed diagnostic results are summarized into a pass/fail indication, and the indication is presented to the repair technician so that proper circuit board replacements can be effected. A failed circuit board is then removed and returned to the factory for repair, often with a written summary of the indications presented to the technician.
A number of limitations exist with the present techniques. First, detailed test results are not reliably and accurately returned with the circuit boards to the repair center. This relates to the practical problems of recording test indications accurately, loss or separation of the diagnostic record during transit of the failed circuit board, etc. Second, once the failed circuit board arrives at the repair center, repair must begin with the minimal information provided about the latest circuit board failure. Third, to proceed with repair, external equipment is required to invoke testing and obtain results, and there is some question whether the original failure can be induced again and identified.